The invention relates to a support for supporting a substrate in a chamber.
In the manufacture of integrated circuits, substrates are processed in a chamber by introducing process gas into the chamber and forming a plasma from the process gas. The substrate is typically supported on a support comprising dielectric covering an electrode. The electrode may be charged to electrostatically hold the substrate, to energize the process gas in the chamber, or both. In addition, a base below the support may comprise channels through which heat transfer fluid may be circulated to heat or cool the substrate.
Newly developed processes for the fabrication of integrated circuits are often performed at high temperatures and in highly erosive gases. For example, processes for etching copper or platinum are conducted at temperatures of from 250 to 600xc2x0 C., compared to temperatures of 100 to 200xc2x0 C. for etching aluminum. The high temperatures and erosive gases thermally degrade the materials used to fabricate the support. The high temperature requirement may be met by ceramic materials, such as aluminum oxide (Al2O3) or aluminum nitride (AlN). However, it is difficult to attach a ceramic dielectric to chamber components which are typically made from metal because the difference in thermal expansion coefficients of the ceramic and metal can result in thermal and mechanical stresses that can cause the ceramic to fracture or chip. Thus It is desirable to have a system for fastening a ceramic support to a chamber without causing excessive thermal stresses between the support and the chamber. In addition, it is desirable to have good or uniform heat transfer rates from the overlying substrate and the underlying structures, to maintain the substrate at uniform temperatures during processing.
Another problem that frequently arises with conventional electrostatic chucks is the difficulty in forming a secure electrical connection between the electrode of the electrostatic chuck and an electrical connector that conducts a voltage to the electrode from a terminal in the chamber. Conventional electrical connectors have spring biased contacts which may oxidize and form poor electrical connections to the electrode. Moreover, electrical connections formed by soldering or brazing the electrical connector to the electrode often result in weak joints that can break from thermal or mechanical stresses. Typically, a hole is machined in the dielectric to expose a portion of the electrode for electrical connection. The machining process causes small microcracks in the dielectric around the electrical connector, especially when the dielectric comprises a ceramic that is brittle. During operation, the support may be repeatedly thermally cycled between room temperature and higher temperatures which may exceed 200xc2x0 C. The mismatch in coefficient of thermal expansion between the dielectric, electrode, and electrical connector can generate thermal stresses that are relieved along the cracks, thereby causing the cracks to propagate. The larger cracks can result in chipping or breakage of the dielectric, or even failure of the electrical connection between the electrical connector and electrode. Also, even smaller microcracks are undesirable because the voltage applied to the electrical connector may dissipate through the microcracks. Thus, it is desirable to have an electrostatic chuck having a secure and reliable electrical connection between the electrode and electrical connector and without microcracks in the dielectric.
Moreover, even when the support is used in low temperature processes, stresses exerted on the electrical connector during assembly and disassembly of the support, as is frequently necessary for cleaning or repairs, can cause the electrical connector to separate from the electrode. Typically, the electrical connector comprises a banana jack which is inserted into a receptacle in the base. The fit between the connectors is tight to ensure good electrical connection, thus considerable force is often needed to insert or remove the connector from its receptacle. This excess force often causes the electrical connector to separate from the electrode or to otherwise move and damage the dielectric. In addition, conventional support fabrication processes often result in a gap between the electrical connector and dielectric which can cause lateral or bending forces on the electrical connector that cause the electrical connector to separate from the electrode.
Thus, it is desirable to have a support that may be used at elevated temperatures, that reduces or alleviates thermal stresses arising from thermal expansion mismatches between the support and other underlying chamber components, and that provides good and uniform heat transfer rates therebetween. It is also desirable to have support and electrode assembly that has a securely bonded electrical connector that can withstand high temperatures and thermal cycling. It is further desirable for the support to provide uniform heat transfer rates. It is also desirable to have an electrode and electrical connector assembly that can withstand repeated connection an disconnection.
In one aspect, support capable of processing a substrate comprises a dielectric enveloping an electrode, a base below the dielectric, and a compliant member between the dielectric and the base. The compliant member reduces thermal stresses between the dielectric and the base, and may also provide good heat transfer rates therebetween.
In another aspect, a chamber capable of processing a substrate, comprises a support comprising a dielectric enveloping an electrode, a base capable of supporting the support, and a compliant member between the support and the base.
In yet another aspect, a method for fabricating a support to support a substrate, comprises the steps of forming a support comprising a dielectric enveloping an electrode, forming a base adapted to support the support, and providing a compliant member between the support and the base.
In one aspect, the support for supporting a substrate in a chamber comprises a ceramic dielectric having a surface capable of receiving the substrate, an electrode below the ceramic dielectric, an electrical connector extending through a hole in the dielectric to connect to the electrode, and a polymer around a portion of the electrical connector.
In another aspect of the present invention, a substrate processing chamber comprises a support having a surface capable of receiving a substrate. The support comprises a ceramic dielectric enveloping an electrode, an electrical connector extending through the ceramic dielectric to connect to the electrode, and a polymer around a portion of the electrical connector. The substrate processing chamber further comprises a gas distributor, a gas energizer, and an exhaust, and a substrate supported on the support is capable of being processed by a process gas distributed by the gas distributor, energized by the gas energizer, and exhausted by the exhaust.
In another aspect, a method of fabricating a support for supporting a substrate comprises the steps of forming a dielectric covering an electrode, the dielectric having a hole which exposes a portion of the electrode, providing an electrical connector in the hole to electrically connect to the electrode, whereby microcracks or gaps are formed between the electrical connector, electrode, and dielectric, and infiltrating a polymer into the microcracks or gaps.